[N:1]1[CH:6]=[CH:5][CH:4]=[C:3]2[C:7](=[O:10])[O:8][CH2:9][C:2]=12.[N:11]1[CH:16]=[CH:15][C:14]([CH:17]=O)=[CH:13][CH:12]=1.C[O-].[Na+].N#N>CO.C(OCC)(=O)CC.O>[N:11]1[CH:16]=[CH:15][C:14]([CH:17]2[C:9](=[O:8])[C:2]3[N:1]=[CH:6][CH:5]=[CH:4][C:3]=3[C:7]2=[O:10])=[CH:13][CH:12]=1To a suspension of 20.27 g (150 mmol) furo[3,4-b]pyridin-5(7H)-one (for preparation see Synthesis 1997, 113) and 14.13 ml (150 mmol) 4-pyridinecarbaldehyde in 120 ml methanol and 75 ml ethyl propionate, 27.8 ml (150 mmol) of a 5.4 M solution of sodium methylate in methanol is added dropwise under ice cooling (and N2 atmosphere). The mixture is heated for 15 min to RT and then for 2 h to reflux temperature. The suspension temporarily goes into solution before a solid forms again. After cooling, 120 ml water is added, before stirring, filtering and washing the product with water. Further product is obtainable from the filtrate by acidification with acetic acid: FAB MS (M+H)+=225.
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